50: Pulmonary Circulation Flashcards

1
Q

What is the total blood volume in pulmonary vasculature?

A

600 ml supine falls by 20%

on standing

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2
Q

What happens to blood volume during forced inspiration?

A

allows an increase to ~1

liter by reducing intrathoracic pressure – opening vessels up

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3
Q

What happens to blood volume during forced expiration?

A

reduces volume to ~300

ml by raising intrathoracic pressure

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4
Q

What is the blood volume in pulmonary capillaries at

any 1 instant?

A

100 mL

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5
Q

What happens to blood volume during heavy exercise?

A

increase from 100 to 150 mL

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6
Q

Increased cross sectional area (and higher resident volume) helps to slow blood down where?

A

Capillaries

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7
Q

Systemic arteries/arterioles

A

thick and have a lot of smooth muscle

divert blood flow to places with max requirements

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8
Q

Pulmonary arteries

A

little smooth muscle and thin walls (very compliant)

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9
Q

Pulmonary capillary

A

walls are very very thin

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10
Q

Why are Pulmonary

Pressures so Low?

A

high pressures would cause blood to drain into lungs

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11
Q

Threshold for edema?

A

25 mm Hg

Hydrostatic pressure is high
enough to push fluid out of
blood into alveoli

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12
Q

How much of the cardiac output does the lung receive?

A

receives 100% of CO

5L at rest
20L during exercise

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13
Q

How much pressure drives flow in the systemic vasculature?

A

100 mm Hg

100 mm Hg/ 5L = 20 units

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14
Q

How much pressure drives flow in the pulmonary circuit?

A

7 mm Hg

7 mm Hg/ 5L = 1.4 units

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15
Q

Pulmonary Vascular Resistance

A

decreases as cardiac output increases

more blood pumped out, pulmonary arterial pressure increases, pulmonary vascular resistance decreases

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16
Q

Pulmonary Arterial Pressure

A

minimal increase during exercise to avoid edema

5 mm Hg increase in
pressure results in 4x the flow b/c of increase CO

17
Q

Recruitment

A

use of already available cross sectional area

18
Q

Distention

A

vasodilation can open up new cross sectional area to further

augment total cross sectional area

19
Q

Extra-alveolar vessels

A

larger and
have a web of interlinking
alveolar vessels between them in
parallel

20
Q

What is the alveolar vessels response to change in lung volume?

A

Alveolar vessels in walls of alveoli

vessels pulled closed as alveoli expand

resistance increases as the lung inflates

like stretching rubber band

21
Q

What is the extra-alveolar vessels response to change in lung volume?

A

sensitive to
radial traction (high
transpulmonary pressures) and pull open as alveoli expand

resistance decreases as the lung inflates

22
Q

Forces promoting fluid filtration

A
↑capillary hydrostatic pressure
↓colloid oncotic pressure
↑surface tension
↓lymphatic drainage
↑ capillary permeability
23
Q

Forces promoting fluid absorption

A

↑ colloid oncotic pressure
↑ air pressure
↓ capillary hydrostatic pressure

24
Q

Regional hypoxia

A

promotes vasoconstriction

less blood to that area of the lung

25
Global hypoxia
all capillary beds and lungs vasoconstrict b/c low oxygen can cause high altitude pulmonary edema
26
Nifedipine
calcium channel blocker prevents high altitude pulmonary edema
27
Where does most ventilation of the lung go?
Base of lung b/c of gravity
28
Where does least ventilation of the lung go?
Apex of lung
29
Which side of heart is low pressure pump?
Right heart
30
Low or No Ventilation
leads to shunt venous blood has gas exchange at alveoli and comes back to left heart deoxygenated
31
Pulmonary Capillary Wedge Pressure (PCWP)
cardiac catheterization to read left atrial pressures Used to determine degree of congestion in pulmonary circuit Heart failure & pulmonary congestion : increased PCWP
32
Increasing Shunt
administering oxygen does not change blood oxygen levels leads to hypoxemia (low oxygen in blood)
33
Lung Zoning
Zone 3: arterial and venous pressure must exceed alveolar pressure so no compression along length of vessel